The BGS Lexicon of Named Rock Units — Result Details

Inferior Oolite Group
Computer Code: INO Preferred Map Code: InO
Status Code: Full
Age range: Aalenian Age (JA) — Bathonian Age (JN)
Lithological Description: Dorset–Somerset (Wessex Basin): Varied succession of bioclastic, peloidal, sandy, ferruginous, argillaceous, bioturbated limestones, with subordinate ooidal limestone, sandstone, limestone conglomerate, lime-mudstone and mudstone beds. Thinly and rubbly bedded with many non-sequences, commonly marked by well-developed hardgrounds, many probably representing considerable breaks. Abundant shelly fauna including ammonites at many levels. A general, but not progressive, increase in ooid content is seen northwards across the region. Cotswolds–Weald: varied succession of ooidal, peloidal, sandy, ferruginous and shelly limestones, with subordinate sandstone, lime-mudstone and mudstone beds (Birdlip Limestone, Aston Limestone and Salperton Limestone formations). South and east Midlands to east Yorkshire: ironstone, ferruginous limestone and sandstone (Northampton Sand Formation), overlain by mudstone, sandy mudstone and siltstone–sandstone (Grantham Formation), and shell-detrital and ooidal limestone (Lincolnshire Limestone Formation).
Definition of Lower Boundary: Worcester Basin–East Midlands Shelf: a disconformity with a change upwards from Lias Group (mudstone with or without sand or sandstone, ferru-ooidal mudstone and limestone beds) into predominantly limestone succession as described in the lithology section. Wessex Basin: passage or sharp change upwards from fine-grained sand and sandstone (Bridport Sand Formation) into limestone succession, by decrease in sand and increase in carbonate cement. Locally (in Mendips area and at depth on the London Platform) unconformably overlies older beds including lower Lias Group, Triassic, Carboniferous and Devonian strata.
Definition of Upper Boundary: In Dorset-Somerset, change from ooidal limestones upward into Fuller's Earth Formation mudstone with beds of finer-grained limestone. In Cotswolds, change from predominantly ooidal limestone (Salperton Limestone Formation) into mudstone (Fuller's Earth Formation) or into sandy fine-grained ooidal limestone (Chipping Norton Limestone Formation) where present, of Great Oolite Group. Generally transitional, but locally an erosive non-sequence marked by a hardground. In North Oxfordshire to Lincolnshire, sharp upward change (unconformity) from fine-grained sandstone (Grantham Formation) or ooidal limestone (Lincolnshire Limestone Formation; where present) into mudstone, siltstone, limestone and sandstone succession of Great Oolite Group (Rutland Formation).
Thickness: 0 to 106 m at outcrop. Generally 4 to 20 m in south Dorset and close offshore, locally thinner or thicker. Thickens north to around 40 m in north Dorset and Somerset (Penn, 1982). 20 to 25 m thick in Wiltshire. South Cotswolds: 10 to 20 m. Thickens east and present at depth in Wessex–Weald Basin (Green, 1992) where up to 120 m thick (Kingsclere No. 1 Borehole, SU45NE1 [SU 4984 5820]). North Cotswolds: 20 to 106 m. Oxfordshire–Northamptonshire: up to 30 m. Lincolnshire: up to 50 m. Offshore: up to 70 m thick in English Channel (Hamblin et al., 1992), up to 257 m thick in St. George’s Channel–Cardigan Bay (Tappin et al., 1994).
Geographical Limits: Outcrop: Dorset, Somerset, Avon, Gloucestershire, Oxfordshire, Northamptonshire, Lincolnshire and Yorkshire (south of Market Weighton High). Subcrop: southern England, apart from interior of London Platform (Parsons, C F, 1980; Sumbler, M G, 1996). Offshore English Channel, Bristol Channel, St. George’s Channel–Cardigan Bay.
Parent Unit: Not Applicable (-)
Previous Name(s): Inferior Oolite (-1341)
Redbourne Group (-1569)
Redbourne Group [Obsolete Name And Code: Use INO And GOG] (RDBN)
Under Oolite Or Oolyte (-2259)
Inferior Oolite Series (-2865)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Quarries at Cleeve Common SSSI, Cleeve Hill, Gloucestershire. Composite Reference Section, quarries together display near complete succession (albeit disjointed) of Birdlip Limestone, Aston Limestone and Salperton Limestone formations in typical, fullest and thickest development. Buckman, S S, 1897; Richardson, L, 1929; Mudge, D C, 1978; Barron, A J M, 1999). 
Type Area  Cotswold Hills: Bath, Avon to Moreton-in-Marsh, Gloucestershire. 
Reference Section  British Geological Survey Stowell Park Borehole, Gloucestershire, 160' 10" (49.02m) to 401' 2" (122.28m). All three of the Cotswold formations (Birdlip Limestone, Aston Limestone and Salperton Limestone) were proved in generally typical development, although the upper, Notgrove and Rolling Bank, members of the Aston Limestone are absent beneath the Vesulian unconformity. Green, G W and Melville, R V, 1956; Sumbler, M G and Barron, A J M, 1995, Sumbler, M G, Barron, A J M and Morigi, A N, 2000. 
Reference Section  Purse Caundle Borehole (ST71NW/7), Dorset, 89.99m to c.134.19m. Proves all five named informal subdivisions of the group of the Shaftesbury district. Barton, C M, et al, 1993; Bristow et al. 1995. 
Reference Section  Nettleton Bottom Borehole (TF19NW/54), Lincolnshire, c.346m to c.392m Proves full thicknesses of all three formations (Lincolnshire Limestone, Grantham and Northampton Sand) in the region. Gaunt, G D, et al, 1992. 
Reference Section  Burton Cliff, Bridport, Dorset. Permanently but inaccessibly exposes the full sequence of the group between the sand of the Bridport Sand Formation below and calcareous mudstone of the Fuller’s Earth Formation above. Lithologies and rich fauna including ammonites can be studied in fallen blocks. Callomon and Cope (1995, pp. 64–67) record a succession of 18 thin limestone beds 4.1 m thick, some subdivided and many with local names, grouped into ‘Lower Inferior Oolite’, ‘Middle Inferior Oolite’ and ‘Upper Inferior Oolite’. Cox and Sumbler (2002, pp. 34-41) revise the base upwards by 0.5 m and avoid the above chronostratigraphical terms. 
Reference Section  Horn Park Quarry, Dorset. Exposes the full sequence of the group between the sand of the Bridport Sand Formation below and calcareous mudstone of the Fuller’s Earth Formation above. The site is famous for its rich fauna of ammonites. Callomon and Cope (1995, pp. 67–69) record a succession of 11 thin limestone beds 4.8 m thick, some subdivided and many with local names, then grouped into ‘Lower Inferior Oolite’, ‘Middle Inferior Oolite’ and ‘Upper Inferior Oolite’. Cox and Sumbler (2002, pp. 47-52) also feature the section but avoid the above chronostratigraphical terms. See also Chandler (1997). 
Reference(s):
Green, G W and Melville, R V. 1956. The stratigraphy of the Stowell Park Borehole (1949-1951). Bulletin of the Geological Survey of Great Britain, No.11, p.1-66. 
Townsend, J. 1813. The character of Moses established for veracity as a historian, recording events from the creation to the deluge. (Bath: Gye; London: Longman.) 
Arkell, W J. 1933. The Jurassic System in Great Britain. (Oxford: Clarendon Press.) 
Fox-Strangways, C. 1892. The Jurassic Rocks of Britain, Vol.1. Yorkshire. Memoir of the Geological Survey of the United Kingdom. 
Woodward, H B. 1894. The Jurassic Rocks of Britain, Vol.4. The Lower Oolitic Rocks of England (Yorkshire excepted). Memoir of the Geological Survey of the United Kingdom. 
Woodward, H B. 1887. The Geology of England and Wales, 2nd edition, p.255, 284-285, 308, 317. (London: George Philip). 
Richardson, L. 1910. The Inferior Oolite and contiguous deposits of the south Cotteswolds. Proceedings of the Cotteswold Naturalists' Field Club, Vol. 17, 63-136. 
Arkell, W J. 1947. The Geology of Oxford. (Oxford: Clarendon Press.) 
Hollingworth, S E, Taylor, J H and others, 1951. The Northampton Sand Ironstone. Stratigraphy, structures and reserves. Memoirs of the Geological Survey of Great Britain, p.3. 
Pringle, J, 1908. On a boring in the Fullonian and Inferior Oolite at Stowell, Somerset. Summary of Progress of the Geological Survey of Great Britain, for 1908. 
Cave, R and Penn, I E. 1971. On the classification of the Inferior Oolite of the Cotswolds. Bulletin of the Geological Survey of Great Britain, No.38, p.59. 
Penn, I E and others. 1980. The Inferior Oolite (Bajocian) sequence from a borehole in Lyme Bay, Dorset. Institute of Geological Sciences, Report No. 79/3. 
Jones, L E and Sellwood, B W. 1989. Palaeogeographic significance of clay mineral distributions in the Inferior Oolite Group (Mid-Jurassic) of southern England. Clay Minerals, Vol.24, No.1. p.91. 
Barron, A J M, Sumbler, M G and Morigi, A N. 1997. A revised lithostratigraphy for the Inferior Oolite Group (Middle Jurassic) of the Cotswolds, England. Proceedings of the Geologists' Association. 
Parsons, C F. 1980. In Cope, J C W (editor). A correlation of the Jurassic rocks of the British Isles. Part Two: Middle and Upper Jurassic. Geological Society of London Special Report, No.15. 
Barron, A J M. 1995. Geological notes and local details for 1: 10 000 Sheet SO91NE (Seven Springs). British Geological Survey Technical Report WA/94/14. 
Barron, A J M. 1999. Geology of the Bishop's Cleeve area (1:10 000 Sheet SO92NE). British Geological Survey Technical Report WA/99/01. 
Buckman, S S. 1897. Deposits of the Bajocian age in the northern Cotswolds: the Cleeve Hill Plateau. Quarterly Journal of the Geological Society of London, Vol.53, 607-629. 
Cox, B M, and Sumbler, M G. 2002. British Middle Jurassic stratigraphy. Geological Conservation Review Series, Vol.26. (Peterborough: Joint Nature Conservation Committee.) 
Gaunt, G D, Fletcher, T P amd Wood, C J. 1992. Geology of the country around Kingston upon Hull and Brigg. Memoir of the British Geological Survey, sheets 80 and 89 (England and Wales). 
Murray, J W. 1968. The Inferior Oolite of the Cotswold scarp, Wotton-under-Edge to Leckhampton. Proceedings of the Bristol Naturalists' Society, Vol.31, 535-549. 
Richardson, L. 1906. Half-day excursion to Leckhampton Hill, Cheltenham. Proceedings of the Cotswold Naturalists' Field Club, Vol.15, 182-189. 
Richardson, L. 1929. The Country around Moreton in Marsh. Memoir of the Geological Survey of Great Britain, Sheet 217, (England and Wales). 
Smith, W. 1815. A memoir to the map and delineation of the strata of England and Wales, with part of Scotland. (London: J Cary). 
Sumbler, M G. 1996. British regional geology; London and the Thames Valley. (4th edition). (London: HMSO for the British Geological Survey). 
Sumbler, M G and Barron, A J M. 1995. Geological notes and local details for 1: 10 000 Sheet SP01SE (Chedworth). British Geological Survey Technical Report, WA/95/73. 
WRIGHT, T. 1860. On the subdivisions of the Inferior Oolite of the south of England, compared with the equivalent beds of that formation on the Yorkshire coast. Quarterly Journal of the Geological Society of London, 16, 1-48. 
Sumbler, M G, Barron, A J M and Morigi, A N. 2000. Geology of the Cirencester district. Memoir of the British Geological Survey, Sheet 235 (England and Wales). 
Mudge, D C. 1978. Stratigraphy and sedimentation of the Lower Inferior Oolite of the Cotswolds. Journal of the Geological Society of London, Vol.135, 611-627. 
Barton, C M, Ivimey-Cook, H C, Lott, G K, and Taylor, R T. 1993. The Purse Caundle Borehole, Dorset: stratigraphy and sedimentology of the Inferior Oolite and Fuller's Earth in the Sherborne area of the Wessex Basin. British Geological Survey Research Report, SA/92/01. 
Bristow, C R, Barton, C M, Freshney, E C, Wood, C J, Evans, D J, Cox, B M, Ivimey-Cook, H C, and Taylor, R T. 1995. Geology of the country around Shaftesbury. Memoir of the British Geological Survey, Sheet 313 (England and Wales). 
Callomon, J H, and Cope, J C W. 1995. The Jurassic geology of Dorset. 51-103 in Field geology of the British Jurassic. Taylor, P D (editor). (London: Geological Society.) 
Anderson, F W, and Dunham, K C. 1966. The geology of northern Skye. Memoir of the Geological Survey of Great Britain, Sheet 80 and parts of sheets 81, 90 and 91(Scotland). 
Donovan, D T, and Hemingway, J E. 1963. Europe; Fasc.3a England, Wales and Scotland; Pt.3a X Jurassic. Lexique stratigraphique international. No. 1. (Paris, France: Centre national de la recherche scientifique.) 
Chandler, R B. 1997. The Graphoceratid ammonite succession in the Aalenian and lowest Bajocian (Middle Jurassic) at Horn Park, Dorset, UK. Proceedings of the Dorset Natural History and Archaeological Society, Vol. 118, 85-106. 
White, H J O. 1923. Geology of the country south and west of Shaftesbury Memoir of the Geological Survey of Great Britain. 
Parsons, C F. 1975. The stratigraphy of the Stony Head Cutting, Bridport. Proceedings of the Dorset Natural History and Archaeological Society, Vol. 96, 8-13. 
Richardson, L. 1907. The Inferior Oolite and contiguous deposits of the Bath-Doulting district. Quarterly Journal of the Geological Society of London, Vol. 63, 383-423. 
Richardson, L. 1916. The Inferior Oolite and contiguous deposits of the Doulting-Milborne Port district (Somerset). Quarterly Journal of the Geological Society of London, Vol. 58, 719-752. 
Richardson, L. 1932. The Inferior Oolite and contiguous deposits of the Sherborne district, Dorset. Proceedings of the Cotteswold Naturalists' Field Club, Vol. 24, 35-85. 
Buckman, S S. 1893. The Bajocian of the Sherborne district: its relation to subjacent and superjacent strata. Quarterly Journal of the Geological Society of London, Vol. 49, 479-522. 
Green, G W. 1992. Bristol and Gloucester region (3rd). British Regional Geology. (London: HMSO for British Geological Survey.) 
Penn, I E. 1982. Middle Jurassic stratigraphy and correlation of the Winterborne Kingston Borehole, Dorset. 53-76 in The Winterborne Kingston Borehole, Dorset, England. Rhys, G H, Lott, G K, and Calver, M A (editors). Report of the Institute of Geological Sciences, No. 81/3. 
Barron, A J M, Lott, G K, and Riding, J B. 2012. Stratigraphical framework for the Middle Jurassic strata of Great Britain and the adjoining continental shelf. British Geological Survey Research Report RR/11/06. 
Hamblin, R J O, Crosby, A, Balson, P S, Jones, S M, Chadwick, R A, Penn, I E, and Arthur, M J. 1992. The geology of the English Channel. British Geological Survey United Kingdom Offshore Regional Report. 
Tappin, D R, Chadwick, R A, Jackson, A A, Wingfield, R T R, and Smith, N J P. 1994. The geology of Cardigan Bay and the Bristol Channel. British Geological Survey United Kingdom Offshore Regional Report. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E102 E103 E127 E142 E144 E157 E161 E170 E271 E279 E280 E281 E296 E171 E172 E185 E186 E199 E200 E201 E202 E217 E218 E234 E235 E236 E237 E251 E252 E253 E264 E265 E268 E270 E297 E312 E313 E327 E341 E342 E343 E081
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